This invention is directed to improvements in means for attenuating the exhaust noise of pneumatically powered tools, such as impact wrenches, grinding tools, and the like.
While the invention may be subject to wide application, it is especially suited for use in pneumatically powered tools of the rotary air vane motor driven type.
In tools of this nature, the motor is driven at high speed by air having a constant pressure of 90 psi. The air spent in driving the vane motor is pulsed from the rotor chamber and exhausted to atmosphere. This pulsating air upon exhausting and expanding to atmosphere would, unless quieted, produce an objectionable noise of pulsating sounds varying in pitch and intensity.
The general objective of this invention is to improve the manner of passage of the exhausting air through the tool so that upon its exhausting to atmosphere the accompanying sound will be attenuated to an acceptable audible level.
In accordance with the invention there is provided a pneumatic tool including an air driven motor comprising a rotor liner defining a rotor chamber having an air driven multiple vane rotor operable therein and having at least one exhaust port through the periphery of the liner for exhaust of driving air from the rotor chamber; a housing for the tool encasing the motor; and a sound attenuating system through which the exhaust air passes to atmosphere, comprising: an annular chamber around the liner into which the exhaust port opens; a leaf spring flap damper disposed in the annular chamber in overlying relation to the exhaust port; and porting communicating the annular chamber to atmosphere; the damper being adapted to flex and oscillate relative to the exhaust port under pressure of air exhausting from the rotor chamber through the exhaust port into the annular chamber.